Glazed units with warm edge

Until recently, aluminium spacer bars were generally used in double glazing.

However, with ever improving window frame and glazing heat conductivity coefficient values, aluminium bars were shown to be the weak point in glass unit construction.

Warm edge

Objectives

Aluminium has significantly greater heat conductivity than the remaining window components. The aluminium spacer bar around the edge of the pane is the last route of excessive heat penetration from the room to the exterior. This effect has been taken into account in the new approach to calculation of the coefficient Uw of the window and has been described with coefficient Psi (Ψ). The solution to this problem may be the application of a spacer bar – called warm edge*, executed from compound insulation material or fine steel.

Warm edge criterion according to EN ISO 10077-1

To the time of establishing clear criteria enabling the definition of the warm edge concept, many spacer bars in glass units were sold on the market, which were indeed warmer than aluminium bars however had incomparably worse properties than correct solutions. According to this bars with improved design standard parameters are those, in which the spacer bar fulfils the following inequality:

Σ (diλi) ≤ 0,007 W/K

where:

di – thickness of partition material

λi – television of conductivity of material in W/mK

Example: 2(d1λ1) + (d2λ2) ≤ 0,007 W/K

The table below shows how particular types of bars fulfill the raised criterion:

Types of bars

Value ∑ (di x λi)

EN ISO 10077-1

Qualification assessment

of spacer bar as “warm edge”

Aluminium

0,1120

negative

Stainless steel
Chromatech

0,0052

positive

Chromatech Ultra

0,0026

positive

Termo TGI

0,0020

positive

Swisspacer Advance

0,0019

positive

Swisspacer Ultimate

0,00002

positive

Multitech G

0,00002

positive

It should be emphasised that the actual effect of a thermal bridge on the edges of glass units mounted in windows depends on the type of spacer bar, heat insulation of the central part of the glass unit and the depth of the pane seating in profile and the coefficient of heat penetration Uf of profile.

Together with the increase in seating depth of the pane the proportion of heat loss of windows through the edge is reduced and minimises the possibility of the occurrence of water vapour. The table presented below compares the coefficient Psi of the most popular bent in corners warm edges* on the market with aluminium spacer bars.

Ug

Construction of glazed units

Window Frame

Type of spacer bar

Psi factor

1,1

4/16/4T Ar

PVC

Aluminium

0,0653

0,7

4T/12/4/12/4T Ar

PVC

Aluminium

0,0663

1,1

4/16/4T Ar

PVC

Stainless steel – Chromatech

0,0511

0,7

4T/12/4/12/4T Ar

PVC

Stainless steel – Chromatech

0,0501

1,1

4/16/4T Ar

PVC

Termo – TGI

0,0401

0,7

4T/12/4/12/4T Ar

PVC

Termo – TGI

0,0381

1,1

4/16/4T Ar

PVC

Chromatech Ultra

0,0391

0,7

4T/12/4/12/4T Ar

PVC

Chromatech Ultra

0,0371

1,1

4/16/4T Ar

PVC

Swisspacer Advance

0,0391

0,7

4T/12/4/12/4T Ar

PVC

Swisspacer Advance

0,0371

1,1

4/16/4T Ar

PVC

Swisspacer Ultimate

0,0321

0,7

4T/12/4/12/4T Ar

PVC

Swisspacer Ultimate

0,0301

1,1

4/16/4T Ar

PVC

Multitech G

0,0311

0,7

4T/12/4/12/4T Ar

PVC

Multitech G

0,0291

1,1

4/16/4T Ar

Wood

Aluminium

0,0713

0,7

4T/12/4/12/4T Ar

Wood

Aluminium

0,0763

1,1

4/16/4T Ar

Wood

Stainless steel – Chromatech

0,0531

0,7

4T/12/4/12/4T Ar

Wood

Stainless steel – Chromatech

0,0541

1,1

4/16/4T Ar

Wood

Termo – TGI

0,0401

0,7

4T/12/4/12/4T Ar

Wood

Termo – TGI

0,0391

1,1

4/16/4T Ar

Wood

Chromatech Ultra

0,0391

0,7

4T/12/4/12/4T Ar

Wood

Chromatech Ultra

0,0381

1,1

4/16/4T Ar

Wood

Swisspacer Advance

0,0391

0,7

4T/12/4/12/4T Ar

Wood

Swisspacer Advance

0,0371

1,1

4/16/4T Ar

Wood

Swisspacer Ultimate

0,0311

0,7

4T/12/4/12/4T Ar

Wood

Swisspacer Ultimate

0,0291

1,1

4/16/4T Ar

Wood

Multitech G

0,0301

0,7

4T/12/4/12/4T Ar

Wood

Multitech G

0,0281

1,1

4/16/4T Ar

Aluminium

Aluminium

0,0802

0,7

4T/12/4/12/4T Ar

Aluminium

Aluminium

0,1102

1,1

4/16/4T Ar

Aluminium

Stainless steel – Chromatech

0,0681

0,7

4T/12/4/12/4T Ar

Aluminium

Stainless steel – Chromatech

0,0661

1,1

4/16/4T Ar

Aluminium

Termo – TGI

0,0491

0,7

4T/12/4/12/4T Ar

Aluminium

Termo – TGI

0,0441

1,1

4/16/4T Ar

Aluminium

Chromatech Ultra

0,0481

0,7

4T/12/4/12/4T Ar

Aluminium

Chromatech Ultra

0,0431

1,1

4/16/4T Ar

Aluminium

Swisspacer Advance

0,0471

0,7

4T/12/4/12/4T Ar

Aluminium

Swisspacer Advance

0,0421

1,1

4/16/4T Ar

Aluminium

Swisspacer Ultimate

0,0361

0,7

4T/12/4/12/4T Ar

Aluminium

Swisspacer Ultimate

0,0311

1,1

4/16/4T Ar

Aluminium

Multitech G

0,0351

0,7

4T/12/4/12/4T Ar

Aluminium

Multitech G

0,0301

1 The data is given on the basis of the IFT Guideline WA-17/12 The data according to guidelines EN ISO 10077 – 1:20073 Data from the supplier aluminum spacer bar

DOWNLOAD PSI (Ψ) FACTOR DATASHEETS – FACADES

From the table above it is shown that the application of plastic or stainless steel warm spacer bars reduces Psi coefficient to 35% in relation to panes with aluminium spacer bar. The effect of this is an increase of window temperature from the side of the room on the contact of frame with glass unit. With the effect that permissible relative air moisture, which in given conditions forms water vapour may due to the application of “warm edges” be higher by approx. 10-15% and shall not cause occurrence of water vapour condensation.

The permissible external minimal temperature is also reduced, at which water vapour condenses on pane surfaces. The table below presents an example of temperature breakdown on window surface from room side of various types of distance bar for Ug=1.1 4/16/4T Ar.

Test conditions

Type of window frame profile

Type of spacer bar

Temperature at edges of internal panes in glass unit [°C]

Δt the edge and in the middle of glass unitinternal pane [°K]

Moisture dew point at edge of internal pane [%]

External temperature 0°C internal temperature +20°C

Wood

Plastic

13,3

4,5

64,1

Stainless steel

12,4

5,2

62,8

Aluminium

10,8

6,8

55,7

PCV

Plastic

13,2

4,7

64,3

Stainless steel

12,5

5,3

62,3

Aluminium

11,1

6,7

56,2

EXAMPLE OF CALCULATION OF Uw COEFFICIENT

Method of calculating coefficient of heat penetration of window Uw, in which the influence of the connection of the frame with the pane is taken into account is indicated in Standard EN ISO 10077 in the form of the following formula:

In order to introduce the above formula we present a calculation example for a single window O32 of dimensions 535 x 1435 mm. The window is executed from the three-cell PCV profile strip of a complete width of frame and window of 125 mm.

Gallery of Swisspacer warm edges colours

Download application and watch gallery of warm edges on your mobile

ADVANTAGES

Reduction of the linear heat leakage bridge on the edges of the glass unit

The properties of thermally insulated glass are also influenced by the linear heat conductivity on the edges. Up to now aluminium spacerbars have been commonly used, which are essential elements of glass units, but they have proved to be poor elements in making double glazed glass units. Aluminium is a much better carrier of heat than the remaining parts of the window construction, so the aluminium spacerbar is the final exit point for heat to move from the interior to the external area. The solution to this problem is to apply a spacerbar known as “ a warm edge”, which is made from highly insulating material or precious steel.

Limitation of condensation of the edges of the glass unit

The solution to this problem is to apply the spacerbar known as “the warm edge”, which is made of highly insulating material or precious steel. The application of the warm edge improves the thermal insulation along the edges, which in turn increases the temperature in this area and reduces the risk of temporary water vapour condensation.

Summary of advantages

Making the choice of warm edge, included in the product range, we are concentrating on:

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